6,395 research outputs found

    Productivity, adjustment costs and R&D investment prices An analysis of a panel of Spanish manufacturing companies

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    This study analyses the role played by adjustment costs and R&D investment prices in total R&D productivity. The results show that on average, for each monetary unit increase in adjustment costs produces a fall in productivity of 0.034 monetary units.R&D, productivity, adjustment costs

    Financial Restrictions, Personal Income Tax (PIT) and Demand for a Permanent Home in a Dynamic Model. An analysis with Panel Data for Spain

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    This paper analyzes the way in which income tax and liquidity determine the purchase or rental of a permanent home in Spain. To do this, we have developed a theoretical dynamic model based on Euler’s equation. This model is verified using a sample from the 1991-1995 Panel of income taxpayers. Results suggest that the degree of financial restriction is the most relevant variable when determining the possibility of purchasing a home, while tax incentives increase their relative weighting once this asset has been acquired. Incentives for renting a home are relatively insignificant particularly for taxpayers who habitually rent their homes.personal income tax, liquidity, permanent home, tax incentives

    Asymptotic normality for the counting process of weak records and \delta-records in discrete models

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    Let {Xn,n1}\{X_n,n\ge1\} be a sequence of independent and identically distributed random variables, taking non-negative integer values, and call XnX_n a δ\delta-record if Xn>max{X1,...,Xn1}+δX_n>\max\{X_1,...,X_{n-1}\}+\delta, where δ\delta is an integer constant. We use martingale arguments to show that the counting process of δ\delta-records among the first nn observations, suitably centered and scaled, is asymptotically normally distributed for δ0\delta\ne0. In particular, taking δ=1\delta=-1 we obtain a central limit theorem for the number of weak records.Comment: Published at http://dx.doi.org/10.3150/07-BEJ6027 in the Bernoulli (http://isi.cbs.nl/bernoulli/) by the International Statistical Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm

    Devonian and Carboniferous pre-Stephanian rocks from the Pyrenees

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    A stratigraphic description of the Devonian and Carboniferous pre-Variscan rocks of the Pyrenees is presented. The successions are grouped into sedimentary domains that replace the "facies area" proposed by previous authors for areas with homogeneous stratigraphy. The description of the sedimentary filling is divided into temporal intervals, where the stratigraphic correlation based in lithological criteria, is supplemented by faunal data, especially conodont finfings. A simple palaeogeographic model of the sedimentation during the Uper Palaeozoic and data related to southern boundary between the Pyrenean basin and the Cantabro-Ebroian Massif are discussed.Ministerio de Educación y Cultura; Project PB98-155

    Stratigraphy and conodont content of the Famennian to Baskhirian rocks from the Quinto Real-Aldudes massif, western Pyrenees

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    Consejo Interinstitucional de Ciencia y Tecnología; DGE PB-98-155

    Silúrico, Devónico y Carbonífero pre- y sin-varisco de los Pirineos

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    Texto enviado junto a la figura publicada en la página 242 del libro, en donde se indica la posición de los diferentes dominios diferenciados en una mapa geológico de los PirineosSe describe la variación en la sedimentación entre el Silúrico y el Carbonífero sibn-varisco en los Pirineos. Una correlación entre las diferentes unidades estratigráficas es propuesta y se revisa la división en dominios

    Learning to learn

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    Redes cerebrales en quejas subjetivas de memoria y deterioro cognitivo leve: caracterización de las etapas de pre-demencia mediante magnetoencefalografía

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    Tesis de la Universidad Complutense de Madrid, Facultad de Psicología, leída el 22/03/2018. Tesis formato europeo (compendio de artículos)La demencia es un cuadro que puede ser originado por múltiples causas, produciendo un deterioro cognitivo muy marcado y limitando la independencia del paciente. La causa más común de demencia es la Enfermedad de Alzheimer (EA) que representa aproximadamente el 60% de los casos totales. Aunque existen numerosos factores que parecen modular el riesgo de desarrollar EA tales como factores genéticos (APOE, PS1, etc.) o variables relacionadas con el estilo de vida (estudios, ocupación, dieta, etc.), la edad es sin duda la variable más influyente y el mayor factor de riesgo ante la aparición de la EA. Por este motivo, el número de personas mayores afectadas por esta enfermedad no ha parado de aumentar durante las últimas décadas, y se espera que aumente su incidencia aún más. Debido al fracaso generalizado de los ensayos farmacológicos, numerosos esfuerzos en investigación se centran ahora en la detección temprana de la EA. El curso de la EA es lento e insidioso, y la acumulación de neuropatología puede comenzar hasta 15 años antes de su diagnóstico. A lo largo de esta etapa preclínica los pacientes atraviesan un estadio conocido como deterioro cognitivo leve (DCL). Esta etapa se caracteriza por alteraciones en uno o varios dominios cognitivos que no genera aún graves alteraciones del funcionamiento diario. Este estadio está altamente asociado al desarrollo posterior de EA y por tanto se considera bajo determinadas condiciones una etapa prodrómica de la enfermedad. Las personas mayores con DCL suelen presentar alteraciones a nivel cerebral o metabólico característicos de la EA, tales como atrofia cortical, alteraciones sinápticas o acumulación de proteínas relacionadas con la fisiopatología de la EA. La literatura científica reciente ha descrito una etapa anterior incluso al DCL que podría asociarse al desarrollo de demencia futuro. Las quejas subjetivas de memoria (QSM) se caracterizarían por la presencia de un sentimiento subjetivo de deterioro cognitivo en ausencia de afectación objetiva, es decir, la evaluación neuropsicológica de estas personas mayores se encuentra en el rango normal. Sin embargo, el estado de la actividad cerebral en esta etapa, o su integridad estructural aún no ha sido apenas descrito. Existen resultados contradictorios con respecto a si la presencia de QSM en personas mayores se asocia a un riesgo más elevado de desarrollar demencia. Además, mientras algunos estudios reportan alteraciones a nivel cerebral compatibles con EA en esta etapa, otros no encuentran tales signos. El objetivo fundamental de esta tesis es la caracterización de las alteraciones en las redes cerebrales en personas mayores sanas, personas mayores con QSM y personas mayores con DCL. El estado actual de la literatura nos permite anticipar la presencia de alteraciones cerebrales relacionadas con EA en el grupo con DCL, sin embargo este trabajo pretende estudiar si dichas alteraciones, o formas más sutiles, se encuentran presentes en el grupo con QSM. Esto nos permitirá en primer lugar clarificar si las QSM tienen alguna relevancia clínica y si se encuentran asociadas a cambios objetivos en la actividad cerebral. Además, se podrá describir el curso exacto de las alteraciones que tienen lugar a lo largo de las etapas preclínicas en la EA gracias a la inclusión del grupo con DCL, caracterizando así en cada estudio las dos etapas que anteceden a la EA descritas a día de hoy...Dementia is a clinical entity producing major cognitive impairment that interferes with daily living activities that can be caused by a variety of conditions. Among them, Alzheimer´s Disease (AD) represents around a 60% of the total dementia cases. AD risk is modulated by multiple variables such as genotype (APOE, PS1, etc.) or lifestyle variables (studies, occupation, dietary patterns, etc.), although age is the most crucial risk factor for AD development. As a consequence, the number of AD patients has rapidly grown over the last few decades and is expected to increase even more dramatically in the near future. Given the poor results obtained in pharmacological trials to cure or slow AD progression, early AD detection is receiving increasing research efforts over the last few years. Considering the slow and insidious progression of AD, brain pathology starts accumulating in the brain as soon as 15 years before clinical symptoms are severe enough to establish an AD diagnostic. Before reaching AD dementia, patients develop mild cognitive impairment (MCI). This stage is characterized by the presence of a significant cognitive impairment affecting one or more domains. However, this cognitive decline does not significantly limit patients’ daily functioning. MCI patients are known to show increased conversion rates to AD with respect to healthy elders and thus this stage is commonly accepted as a prodromal stage of AD according to recent MCI criteria. MCI patients are known to exhibit AD-like brain and metabolic alterations such as cortical atrophy or AD-related protein accumulation. Recent scientific literature has described a stage preceding MCI which could be associated with future dementia development. Subjective cognitive decline is defined by the presence of a subjective feeling of cognitive worsening in the absence of objective impairment in classical neuropsychological assessment. However, the integrity of brain activity or structure has been scarcely described yet. Furthermore, there exist some contradictory results regarding whether the presence of cognitive concerns is truly related to increased dementia risk. In the same vein, some studies have found brain alterations in SCD patients resembling of those associated with AD while others failed to find such signs. The main objective of this thesis is characterizing brain network alterations in healthy elders, elders with SCD and elders with MCI. The current state-of-the-art lets us anticipate the presence of brain disruption in the MCI group, nonetheless, this work aims to provide evidence of whether similar alterations are already present in the SCD stage. The results presented in this thesis will clarify the clinical relevance of SCD by discerning whether cognitive concerns are truly mediated by network disruption or not. Moreover, the exact course and development of electrophysiological brain alterations during the preclinical stages of the disease will be described by including also MCI patients. By including these three groups we will be able to characterize brain function in the different AD preclinical stages considered in current literature...Fac. de PsicologíaTRUEunpu
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